In the field of vehicles such as automobiles, there is conventionally known an insulated wire including a stranded wire conductor that is formed of a plurality of conductor element wires twisted together and an insulator that covers the outer circumference of the stranded wire conductor.
As the stranded wire conductor, specifically, Patent Document 1 (JP-A-2008-159403) discloses a stranded wire conductor including a stainless element wire and a plurality of bare copper element wires that are twisted together on the outer circumference of the stainless element wire. Further, the document describes a technique for softening copper in which the bare copper element wires is subjected to heat treatment to improve the elongation deteriorated by work-hardening resulted after the bare copper element wires were twisted together and subjected to circular compression.
Meanwhile, as a material for the insulator, for example, a fluororesin such as a tetrafluoroethylene resin (PTFE) and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polypropylene (PP) and the like are known.